Dark chocolate intake buffers stress reactivity in humans.

Baseline levels of the respective parameter were controlled. To the Editor: Dark chocolate consumption substantially lowers cardiovascular mortality due to the high content of polyphenolic flavonoids (1), but underlying mechanisms remain unclear. Psychosocial stress is a risk factor that supposedly promotes cardiovascular disease (CVD) by inducing hypothalamus-pituitaryadrenal (HPA) axis and sympathetic nervous system (SNS) stress responses implicated in the increase of CVD risk, either by direct effects or by inducing adverse changes in intermediate biological risk factors, or both (2). Animal studies suggest that flavonoid administration may protect from adverse stress effects by reducing stress responses including HPA axis activation (3). A human study in healthy men assessed endocrine stress reactivity after 6 weeks of consuming either flavonoid-containing tea or flavonoid-free placebo tea and found a faster decline of cortisol levels after a moderate mental stress task in the active tea group (4). Here, we investigate whether a single administration of dark chocolate buffers endocrine reactivity to acute psychosocial stress in healthy men and whether this effect relates to plasma levels of the flavonoid epicatechin. Moreover, we wanted to determine whether this effect would be peripheral (by measuring the adrenal gland hormones cortisol and epinephrine) or more central (by assessing adrenocorticotropic hormone [ACTH], norepinephrine, and cognitive stress appraisal). We used a placebo-controlled, between-subject study design with healthy, medication-free, non-smoking men (20 to 50 years of age) who were age-matched assigned to the experimental dark chocolate group (n 1⁄4 31) or the placebo control group (n 1⁄4 34). The dark chocolate (“Noir 72%”; Chocolat Frey AG, Buchs/Aargau, Switzerland) contained 281 kcal and 125 mg of epicatechin per serving of 50 g. The optically identical placebo chocolate (310.5 kcal and 0 mg epicatechin per 50-g serving) was a flavonoid-free white chocolate that was dyed and flavored to match the color, appearance, and smell of the dark chocolate. After subjects ate a standardized breakfast at 10:00 AM, a venous catheter was inserted at 10:45 AM, followed 45 min later by the first saliva and blood sampling, with subsequent administration of 50 g of dark or placebo chocolate. Subjects underwent the psychosocial stressor 2 h after chocolate ingestion, when we expected plasma flavonoid levels to peak. We applied the Trier Social Stress Test (TSST), which combines a 3-min preparation phase after a short introduction, a 5-min mock job interview, and a 5-min mental arithmetic task in front of an audience. As stress hormones secreted from the adrenal gland and thus in the periphery only we measured the HPA axis hormone cortisol (secreted by the adrenal cortex) and the SNS hormone epinephrine (secreted by the adrenal medulla). As hormones indicating a more central stress effect, we measured the HPA axis hormone ACTH secreted by the anterior pituitary and the SNS hormone norepinephrine released both as neurotransmitter from sympathetic nerve endings and to a lesser extent as stress hormone from the adrenal medulla. Saliva (Salivette; Sarstedt, Rommelsdorf, Germany) and